Rotary mill

Abstract

A rotary mill for reduction of ore to particles is described. The rotary mill comprises a primary reduction chamber, a secondary reduction chamber and an outlet chamber. Material entering the primary reduction chamber is deflected by an impact rotor, which shatters the material and sends the resulting particles into a plurality of shatter bars. The shatter bars further reduce these particles and deflect them back towards the rotor so that the reduced particles encounter newly shattered material, causing further attrition. In addition, the rotary mill includes an exhaust fan arranged to generate an airflow from the primary reduction chamber, through the secondary reduction chamber and into the outlet chamber. This airflow carries the reduced particles into the secondary reduction chamber wherein the particles are thrown against reduction means. The reduction means are positioned between the secondary reduction chamber and the outlet chamber such that only particles below a certain size enter the outlet chamber. Material of sufficiently reduced size enters the outlet chamber wherein it is separated into fine particles and heavier particles. Specifically, the heavier particles fall out of the airflow and gather at the base of the outlet chamber until a sufficient weight accumulates to open the balance door which expels the heavy material from the rotary mill.

I claim: 
     
       1. An apparatus for fragmenting solid materials into particles comprising: a housing;   a first impact chamber defined within the housing and having a feed opening;   a feed system positioned above the feed opening of the first impact chamber for feed of solid materials into the impact chamber;   a rotor having impact hammers at its periphery located within the first impact chamber for rotation about an axis of the rotor transverse to the feed opening, the rotor being positioned relative to the feed opening such that said impact hammers impact and deflect the solid materials entering through the feed opening, thereby fragmenting the solid materials to form particles;   a plurality of shatter bars located within the first impact chamber arranged such that the shatter bars contact the deflected solid materials, thereby further fragmenting the solid material into said particles;   a second impact chamber defined within the housing downstream of the rotor;   means for connecting the first impact chamber and the second impact chamber such that the particles pass from the first chamber to the second chamber under momentum from the rotor;   the rotor being arranged such that rotation thereof generates an air flow acting to carry the materials from the first impact chamber into the second impact chamber;   an outlet chamber connected to the second impact chamber for receiving the particles therefrom;   a plurality of reduction means located between the second impact chamber and the outlet chamber, positioned such that only particles below a predetermined size pass through the reduction means and into the outlet chamber;   a fine particle outlet duct connected to the outlet chamber and arranged to receive the particles therefrom;   a bottom discharge for allowing release of heavier particles from a bottom of the outlet chamber;   an exhaust fan connected to the fine particle outlet duct for generating an additional airflow through feed opening into the first impact chamber and from the first impact chamber into the second impact chamber;   and a balanced flow control door which normally doses the bottom discharge such that substantially all air exiting the outlet duct passes into the first impact chamber through the feed opening and which is arranged such that it is opened under the weight of the heavier particles to allow said release of the heavier particles through the bottom discharge.